stepjue/ahkab

a SPICE-like electronic circuit simulator written in Python

# ahkab

a SPICE-like electronic circuit simulator written in Python

The code should be easy to read and modify, the main language is Python 2.x and it is platform-independent.

News!

• Ahkab v0.10 released, including several bugfixes and improvements. Check out the release notes for more!
• The whole codebase has been going through a (yet incomplete) refactoring and documenting effort. The new documentation is available on RTD.
• Tests have been added to the code base, to weed out bugs and have a consistent way to check for regressions. If you have tests you would like to suggest, please send a PR my way.
• My resources are limited these days, so the much-needed work is proceeding slowly, albeit hopefully steadily. If you are interested and you would like to contribute to refactoring or documenting a particular feature, it would be very welcome.

Supported simulations:

• Numeric:
  • Operating point, with guess computation to speed up the solution. See example: Downscaling current mirror
  • DC sweep
  • Transient analysis, available differentiation formulas: implicit Euler, trapezoidal, gear orders from 2 to 5. See for example the simulation of a Colpitts Oscillator.
  • AC analysis
  • PZ analysis (git-tree only)
  • Periodic steady state analysis of non-autonomous circuits, time domain shooting and brute-force algorithms.
• Symbolic:
  • Small signal analysis, AC or DC, with extraction of transfer functions, DC gain, poles and zeros. Various symbolic analysis examples on this page.

The results are saved to disk, plotted or printed to stdout and can be read/processed by the most common tools (eg. Octave, gnuplot, Matlab, gwave and others)

##Install##

The program requires:

• the Python 2 interpreter (at least v.2.6, and Python3 is in the works),
• numpy, matplotlib and sympy.

If you need more information about the dependencies, check the Install notes.

##Usage##

• ahkab can be run within Python scripts as a library.

###Example###

from ahkab import new_ac, run
from ahkab.circuit import Circuit
from ahkab.plotting import plot_results # calls matplotlib for you
import numpy as np

# Define the circuit
cir = Circuit('Butterworth 1kHz band-pass filter')
cir.add_vsource('V1', 'n1', cir.gnd, dc_value=0., ac_value=1.)
cir.add_resistor('R1', 'n1', 'n2', 50.)
cir.add_inductor('L1', 'n2', 'n3', 0.245894)
cir.add_capacitor('C1', 'n3', 'n4', 1.03013e-07)
cir.add_inductor('L2', 'n4', cir.gnd, 9.83652e-05)
cir.add_capacitor('C2', 'n4', cir.gnd, 0.000257513)
cir.add_inductor('L3', 'n4', 'n5', 0.795775)
cir.add_capacitor('C3', 'n5', 'n6', 3.1831e-08)
cir.add_inductor('L4', 'n6', cir.gnd, 9.83652e-05)
cir.add_capacitor('C4', 'n6', cir.gnd, 0.000257513)
cir.add_capacitor('C5', 'n7', 'n8', 1.03013e-07)
cir.add_inductor('L5', 'n6', 'n7', 0.245894)
cir.add_resistor('R2', 'n8', cir.gnd, 50.)

# Define the analysis
ac1 = new_ac(2.*np.pi*.97e3, 2.*np.pi*1.03e3, 1e2, x0=None)

# run it
res = run(cir, ac1)

# plot the results
plot_results('5th order 1kHz Butterworth filter', [('|Vn8|',"")], res['ac'],
             outfilename='bpf_transfer_fn.png')

• or stand-alone with a netlist file, the syntax being:

  $ python ahkab -o graph.dat <netlist file>

See ahkab --help for command line switches.

###Documentation###

Refer to the netlist syntax page for how to write the netlist files that describe the circuit. Experience with running SPICE or other commercial simulators can be useful.

The latter option is shown briefly in the Python API wiki page. The code comes with docstrings associated with most functions, type help(ahkab.function_name).

How this project was born

This project was born when I was an enthusistic undergrad, apparently with plenty of free time, attending "Simulazione Circuitale" (Circuit Simulation) taught by Prof. A. Brambilla back in Italy at the Polytechnic University of Milan.

I am grateful to prof. Brambilla for teaching one of the most interesting courses of my university years. -GV

Contributors

Giuseppe Venturini, Ian Daniher, Rob Crowther.

Bugs and patches

Note that I often add new functionality at the expense of breaking stuff. Most likely I will introduce a new feature even if that means breaking a couple of others. It should get fixed soon, but if you have a bit of time to spare, you can send me a pull request or a patch. :)

Does it work? Bugs? Do you have patches? Did you run some noteworthy simulation? Let me know! Feedback is very welcome, my email address is available after a captcha.